from threading import Thread
import threading
import time
class Sub_T(Thread):
    def run(self):
        for i in range(3):
            time.sleep(1)
            print(f"线程{threading.current_thread().name}，正在执行，{i}")
if __name__ == '__main__':
    start = time.time()
    print("主线程开始执行")
    lst = [Sub_T() for i in range(2)]
    for item in lst:
        item.start()
    for item in lst:
        item.join()
    print("主线程执行完毕")
    print("耗时", time.time() - start)